The invention concerns apparatus for growing cell cultures wherein the cultures are located within at least one liquid nutrient medium in a closed container, the nutrient medium or media being fed to the container by at least one supply line connected to a pump and a gas being supplied to the headroom above the liquid level in the closed container, such as oxygen, nitrogen, air or the like, of which the pressure is kept constant in the head room.
Nutrient media must be supplied because the nutrient medium in the container must be periodically replaced. The evacuation of the excess liquid hence must be provided for simultaneously with the supply.
In this respect it is already known to insert a pump into an evacuation line which removes as much liquid from the container as is being fed to it through the nutrient media supply line. It is further known in this regard to so control the pumps mounted in the supply and evacuation lines by a level regulating means that the evacuated amount of liquid always matches as closely as possible the one being introduced.
It is already known with respect to such level control to probe the liquid level by a sensor or else to weigh the container and to use the test values so obtained to start or shut off the pumps.
In all these known devices, the drawback is incurred that by using a pump in the evacuation line the free cells being evacuated with the nutrient liquid may be injured or destroyed by the pump, these injured cells possibly so degrading the product sought (biological molecules, proteins etc.) that either the product is not obtained at all or product manufacture becomes uneconomical.